This specification relates to cloud computing.
In cloud computing, data can be distributed to and processed by a system of multiple computers connected by one or more communications networks. Each computer processes a portion of the data. The computers can process the data in parallel. Such a distributed system can handle web-oriented and data-intensive applications deployed in a virtualized environment. For example, a distributed system can be configured to perform functions of a relational database management system (RDBMS) over the Internet. Some challenges of a distributed system replacing a conventional RDBMS include performing data synchronization among multiple computers in the system, achieving low latency over a wide area network (WAN), scalability, and handling different schemas of multiple users.